The invention relates generally to lubrication systems for internal-combustion engines, and more specifically to lubrication systems for use in motorcycle engines.
One example of a lubrication system for use with an internal-combustion engine is disclosed in U.S. Pat. No. 5,588,405 issued to Atsushi Sawa. The engine includes a gearbox incorporated into the crankcase. Oil ducts deliver lubricating oil to the camshaft and to the gears within the gearbox. The oil is circulated within the engine between the crankshaft, various oil-consuming devices, and an oil sump by an oil pump.
Additional lubrication is required in engines that have manual gearboxes. In particular, in manual gearboxes the gears are moved or shifted by gearshift sleeves and gearshift forks. The gearshift sleeves are moved axially along one or more shafts by one or more gearshift forks. Friction between the gearshift sleeves, the gearshift forks, and the shafts can cause premature wear in the gearbox. It is therefore desirable not only to supply lubricating oil to the gears and to the shafts within the gearboxes but also to supply lubricating oil to the gearshift sleeves and to the gearshift forks.
The present invention includes an apparatus and a method for lubricating the gearshift sleeves and the gearshift forks. In conventional engines, oil or some other lubricant is cycled through the engine from the oil sump through the cylinder head and the other oil-consuming devices and back to the oil sump. In the present invention, some of the oil is diverted from this lubrication cycle to the gearbox to provide lubrication for the gears, shafts, gearshift sleeves, gearshift forks, and other elements within the gearbox. Additionally, the present invention requires few additional components because the present invention utilizes the existing lubrication cycle, including the oil pump and oil sump to supply oil to the gearbox.
In the present invention, a shaft extends into a gearbox. A number of gearshift sleeves are arranged axially along the shaft adjacent a number of gears. A corresponding number of gearshift forks are arranged axially along the shaft within the gearbox for shifting the gearshift sleeves along the shaft. The gearshift forks are configured to engage the gearshift sleeves and to move the gearshift sleeves along the shaft. The gearshift sleeves then move the gears within the gearbox along the shaft. Oil enters the gearbox through an oil duct, which extends through the wall of the gearbox. Preferably, an oil intake channel extends through the cylinder head housing and into the wall of the gearbox. A transverse oil duct is preferably situated in the wall of the gearbox and receives oil from the oil intake channel and distributes the oil through the oil bores to the gearbox. Preferably, a plurality of oil ducts extend into the gearbox to direct oil into the gearbox and to direct oil onto the gearshift forks and onto the gearshift sleeves.
A rib preferably extends from the wall of the gearbox into a cavity in the gearbox. The rib is preferably contoured to closely engage the plurality of gears within the gearbox. As the gears and gearshift sleeves rotate about the shaft, the gears, and the gearshift sleeves fling oil against the gearbox wall. The rib collects at least some of the oil that is flung off of the gears and the gearshift sleeves as they rotate within the gearbox. The rib then directs this oil back onto the gearshift forks and the gearshift sleeves, thereby lubricating the gearshift forks and the gearshift sleeves. Preferably, the rib is positioned adjacent at least one of the oil ducts so that oil which exits the oil ducts flows across the rib. In this manner, the rib can direct the oil from the oil ducts onto the gearshift forks and the gearshift sleeves.
In a second aspect of the present invention, the gearbox includes two relatively parallel shafts. Gears and gearshift sleeves are affixed to both shafts so that the gears intermesh, transmitting power from the first shaft to the second shaft. Preferably, a first and a second rib are positioned within the gearbox with one rib adjacent each of the first and second shafts. In this manner, the first rib can direct oil onto the first shaft and the elements which are mounted on or relatively near the first shaft such as the gearshift forks and the gearshift sleeves. In a similar manner, the second rib can direct oil onto the second shaft and the elements which are mounted on or relatively near the second shaft such as the gearshift forks and the gearshift sleeves. Preferably, the second rib is positioned adjacent at least one oil duct so that oil which exits the oil ducts flows across the second rib. In this manner, the second rib can direct oil from the oil ducts onto the gearshift forks and the gearshift sleeves of the second shaft.
Preferably, a plurality of projections extend from the ribs into the gearbox, each projection being adjacent a gearshift sleeve and/or a gearshift fork. In this manner, the oil, which is collected on the ribs, drains off of the ribs and is then directed onto the gearshift sleeves and the gearshift forks by the projections. Additionally, some of the oil that is flung off of the gears and the gearshift sleeves contacts the projections. The projections direct this oil onto the gearshift sleeves and the gearshift forks.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.